Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 81: Graphene: Transport incl. Spin Physics and Magnetic Fields I
HL 81.7: Vortrag
Donnerstag, 29. März 2012, 16:30–16:45, ER 270
Relaxation dynamics in Landau-quantized graphene probed in the mid-infrared range — •Martin Mittendorff1, Stephan Winnerl1, Harald Schneider1, Manfred Helm1, Milan Orlita2, Marek Potemski2, Mike Sprinkle3, Claire Berger3, and Walter A. de Heer3 — 1Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ionebeamphysics and material research, Germany — 2Grenoble High Magnetic Field Laboratory, France — 3Georgia Institute of Technology, Atlanta, USA
In contrast to conventional semiconductors the Landau levels (LLs) in graphene are not equidistant. This feature allows us to investigate a single LL transition selectively. By applying magnetic fields of up to 7 T we could investigate three different transitions at a fixed wavelength of 16.5 µm via pump-probe measurements. By varying the magnetic field the photon energies were brought into resonance with the different transitions. For the transition LL0(−1)−>LL1(0) we could not only observe an increase of the pump-probe signal by a factor of 2.5 but also a decrease of the relaxation time from 20 ps to 5 ps. Interestingly, the reduced relaxation time is observed in a wider range of magnetic fields than the increase of the signal amplitude. Additionally the minimum of the relaxation time is shifted in respect to the maximum signal. For the transitions LL−1(−2)−>LL2(1) and LL−2(−3)−>LL3(2) we could only observe an slight increase of the pump-probe signal.